Juha Pekka Lunkka

New radiocarbon dates from Finnish mammoths indicating large ice-free areas in Fennoscandia during the Middle Weichselian

New radiocarbon dates from Finnish subfossil mammoth material (Mammuthus sp.), transported by glacial ice, range in age from ca. 32000 to ca. 22500 yr BP. These results suggest that there was a larger ice-free area in Fennoscandia during the Middle Weichselian than previously assumed. In addition, two dates are also presented for bones found in clay with a different transport history. Copyright

Glaciation of Finland

This chapter discusses the glaciation history of Finland. According to the Finnish till stratigraphy, there are six stratigraphically significant till beds in Finnish Lapland. The uppermost three represent Weichselian tills. The so-called Till Bed IV was laid down during the Saalian glaciation, and the two lowermost till beds that underlie a Holsteinian peat stratum may represent Elsterian or pre-Elsterian tills. Although Elsterian or pre-Elsterian tills are preserved at scattered localities in northern Finland, there is no conclusive evidence for pre-Saalian tills in Southern Finland. In southern Finland, there are no end-moraines related to the early or middle Weichselian ice advances. Information on the extent of the ice streams is limited and based on the distribution of interstadial organic remnants and till stratigraphy. The stratigraphy of the Early and Middle Weichselian substages in Northern Finland is based on the correlation of interstadial organic deposits, till stratigraphy and till-covered glaciofluvial landforms. Many stratigraphically important areas and key localities are situated in the ice divide zone in Central Lapland. It appears that the processes of glacial erosion and deposition were ex-ceptionally weak in this zone.

The Glaciation of Finland

Abstract Middle Pleistocene Glaciations . In Lapland and western Finland there are sites where till or glaciofluvial deposits underlie Eemian organic sediments. Many of them are correlative to the Saalian glaciation. At Naakenavaara a Holsteinian peat is underlain by the Elsterian till unit. These sites provide the basis for the general Quaternary stratigraphy of Finland. Late Pleistocene Glaciations . After the Eemian Stage interglacial two Early Weichselian stadials and two interstadials (Brorup, MIS 5c and Odderade, MIS 5a) have been found. The extent of the Middle Weichselian ice sheet is still unknown. Finland was ice covered during Late Weichselian Substage and was completely deglaciated by 10 ka ago.

Land-ocean changes on orbital and millennial time scales and the penultimate glaciation

Past glacials can be thought of as natural experiments in which variations in boundary conditions influenced the character of climate change. However, beyond the last glacial, an integrated view of orbital- and millennial-scale changes and their relation to the record of glaciation has been lacking. Here, we present a detailed record of variations in the land-ocean system from the Portuguese margin during the penultimate glacial and place it within the framework of ice-volume changes, with particular reference to European ice-sheet dynamics. The interaction of orbital- and millennial-scale variability divides the glacial into an early part with warmer and wetter overall conditions and prominent climate oscillations, a transitional mid-part, and a late part with more subdued changes as the system entered a maximum glacial state. The most extreme event occurred in the mid-part and was associated with melting of the extensive European ice sheet and maximum discharge from the Fleuve Manche river. This led to disruption of the meridional overturning circulation, but not a major activation of the bipolar seesaw. In addition to stadial duration, magnitude of freshwater forcing, and background climate, the evidence also points to the influence of the location of freshwater discharges on the extent of interhemispheric heat transport.

Sedimentation of the Late Miocene Bahe Formation and its implications for stable environments adjacent to Qinling mountains in Shaanxi, China

Abstract An important key site along the Bahe River in the Lantian area, Shaanxi Province, northern China exposes a conformable sedimentary sequence that records the transition from early Late Miocene fluvial sediments into Late Miocene and Pliocene aeolian Red Clay, and finally into Pleistocene loess. Although the Red Clay and Pleistocene loess in northern China have been intensively studied over the years, the Bahe Formation, beneath the Red Clay in the Lantian area, has been less well studied. Here we present the preliminary results of a detailed lithostratigraphical investigation of the Bahe Formation on the northern slopes of the Bailuyuan Plateau and discuss the style of sedimentation during its deposition. The Bahe Formation in the Lantian area, is composed of fluvial and lacustrine deposits laid down in the Weihe Graben during the Late Miocene. Six main facies assemblages have been distinguished: (1) massive or crudely bedded conglomerates, (2) cross-stratified conglomerate and sandstone deposits, (3) minor sandstone deposits, (4) fine-grained deposits, (5) gritty mudstone and sandstone deposits and (6) marl deposits. These assemblages represent the deposits of active channels, crevasse splays, sheet floods, and floodplains with paleosols and lakes. Thick and laterally pervasive units of fine-grained sediments, formed as suspension fall-out on the floodplain, indicating low-energy conditions and a relatively gentle surface gradient in the area, are by far the most common sedimentary component. Channel-related sandstones and conglomerates indicate that the rivers had a low-sinuosity and were braided, to anastomosing types. The Bahe fluvial system operated for several million years in a tectonically inactive setting in a vegetated area under a relatively arid climate. This environmental interpretation is consistent with that derived from the interpretation of the vertebrate fossil fauna recovered from the sediments.

Valdaian glacial maxima in the Arkhangelsk district of northwestern Russia

Abstract The marginal configurations and ages of the Valdaian (Weichselian) glacial maxima in northern Russia have hitherto not been well established, thus, numerous versions of the Last Glacial Maximum (LGM) positions of the Scandinavian Ice Sheet are known ( Fig. 1B ). New data on ice sheet growth and decay indicate at least three glacial maxima during the Late Pleistocene each with individual spreading centres and different ages. Results of modern investigations in the Arkhangelsk region, conducted by the authors, are compared with an analysis of previous data on the Late Quaternary geology of Northwest Russia, which comprises a thorough presentation of Russian literature on this subject. This has allowed us to question and revise former models on Valdaian glaciation history and ice-marginal positions in a major part of the Russian North. An Early-Middle Valdaian (c. 70 ka BP) glaciation from the east and southeast, possibly originating on the Timan ridge, crossed the Pyoza River basin and reached the White Sea coast along the Bay of Mezen. The southern terminus of the ice sheet is probably found along parts of the Mezen River ( Fig. 2A,B ). The presence of an Early-Middle Valdaian Scandinavian glaciation, which covered the Arkhangelsk region and in neighbouring areas of Karelia and Vologda is not supported by geological data. In the Middle Valdaian (c. 70 ka BP) an ice sheet from the Barents-Kara Sea flowed from the north, northeast and reached the lower Pyoza River and the south and western shores of Mezen Bay on the White Sea coast. The terminal formations of its maximal stage stretch from west to east just north of Pyoza River and then run marginal to the Timan ridge from the north joining with the Markhida end-moraines on the Pechora Lowland ( Fig. 2A, B ). During the Late Valdaian, the Scandinavian Ice Sheet occupied the northwestern part of the Arkhangelsk region around 19-17 ka BP. The limit of this Late Valdaian glacial maximum runs from the White Sea shore of the Kanin Peninsula in the north, along the Kuloi River south of Mezen to the Middle Pinega River, crossing the rivers Severnaya Dvina and Vaga near the villages of Cherevkovo and Ust-Padenga. The glacial boundary bordered the Melovian and Nyandoma high ground and continued southwestwards to Lake Kubenskoe in the Vologda region. The Pyoza, Mezen and Vashka river basins remained ice-free during the Late Valdaian time, this area being covered by fluvial flood plains, with abundant evidence of permafrost and lakes. The latter have yielded pollen evidence indicating an arctic to subarctic environment between 18-10 ka BP ( Fig. 2A, B ).

DynaQlim – Upper Mantle Dynamics and Quaternary Climate in Cratonic Areas

The isostatic adjustment of the solid Earth to the glacial loading (GIA, Glacial Isostatic Adjustment) with its temporal signature offers a great opportunity to retrieve information of Earth’s upper mantle to the changing mass of glaciers and ice sheets, which in turn is driven by variations in Quaternary climate. DynaQlim (Upper Mantle Dynamics and Quaternary Climate in Cratonic Areas) has its focus to study the relations between upper mantle dynamics, its composition and physical properties, temperature, rheology, and Quaternary climate. Its regional focus lies on the cratonic areas of northern Canada and Scandinavia.

Mikulino and Valdai palaeoenvironments in the Vologda area, NW Russia

Abstract Nine representative sediment sequences and pollen diagrams obtained during the Quaternary mapping programme carried out by the Geological Expedition (St. Petersburg, Russia) between 1960s and 1980s are presented from the Vologda area, NW Russian Plain, covering the time span from the Moscow cold (Saale) stage into the Late Valdai (Weichsel) substage. This work was done in order to shed light on the evolution of palaeoenvironments, vegetation and climate in the area. The results suggest that two major depressions in the Vologda area, namely the Mologa–Sheksnian and Prisukhonian basins, witnessed lake level fluctuations that were most likely closely linked to climatic fluctuations. It is suggested that during the Mikulino (Eem) thermal optimum most of the lowland areas were dry land. However, during the Early and Middle Valdai, the large depressions started to flood as a result of wet and cold climate. This caused the accumulation of lacustrine and also lacustrine–alluvial and lacustrine–bog sediments into the basins. The Valdai forest composition varied between closed spruce–birch forests and treeless tundra. Lakes persisted throughout the Valdai stage including the extremely dry last glacial maximum (LGM)-time when the Scandinavian Ice Sheet dammed the northbound rivers in the Vologda area.

Foreword to the Special Issue: Arctic Palaeoclimate and Its Extremes (APEX)

The recent mass loss of the Greenland ice sheet (Chen et al. 2006), the observed increases in the velocity of its fast-flowing outlets (Luthcke et al. 2006) and the melting of the permafrost demonstrate the profound changes occurring in the Arctic region as a result of global warming (ACIA 2005). This is corroborated by systematic satellite monitoring that shows there has been a progressive decrease in the extent of sea ice over the last 30 years, with a record low in 2007 (Comiso et al. 2008). Forward modelling predicts accelerated rates of sea-ice disintegration and the almost complete disappearance of Arctic Ocean summer sea-ice cover within this century. It is clear that the environment in the Arctic is changing at a pace not previously monitored by humankind. It is equally clear, however, that to place the current changes in a millennial time perspective, we need to know more about the Pleistocene natural variability and amplitude of, for example, the Greenland ice sheet, Arctic Ocean sea ice and permafrost. Such a longer time perspective can only be established through international collaborative and multidisciplinary studies of nature’s own archives, such as marine and terrestrial stratigraphic records, sediment distribution and landforms.